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_interlockedbittestandset, _interlockedbittestandset64

Visual Studio 2010

Updated: March 2011

Microsoft Specific

Generate the lock bts instruction, which examines bit b of the address a and returns its current value before setting it to 1.

Copy 
unsigned char _interlockedbittestandset(
   long *a,
   long b
);
unsigned char _interlockedbittestandset64(
   __int64 *a,
   __int64 b
);
[in] a

A pointer to the memory to examine.

[in] b

The bit position to test.

The bit at the position specified before it is set.

Intrinsic

Architecture

_interlockedbittestandset

x86, x64

_interlockedbittestandset64

x64

Header file <intrin.h>

As a result of the lock bts instruction, the bit is set to 1. The operation is atomic.

These functions behave as read-write memory barriers. For more information, see _ReadWriteBarrier.

This routine is only available as an intrinsic.

Date

History

Reason

March 2011

Clarified the return value.

Information enhancement.
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Older SDKs have an error 
Error    1    error C2733: second C linkage of overloaded function '_interlockedbittestandset' not allowed    $VCDIR\include\intrin.h    944
Error    2    error C2733: second C linkage of overloaded function '_interlockedbittestandreset' not allowed    $VCDIR\include\intrin.h    945
This is due to the fact that WinNT.h and intrin.h both declare those functions (set and reset and their 64 bit counterparts). One workaround is this:

#if _MSC_VER >= 1400
//  Following 8 lines: workaround for a bug in some older SDKs
#   pragma push_macro("_interlockedbittestandset")
#   pragma push_macro("_interlockedbittestandreset")
#   pragma push_macro("_interlockedbittestandset64")
#   pragma push_macro("_interlockedbittestandreset64")
#   define _interlockedbittestandset _local_interlockedbittestandset
#   define _interlockedbittestandreset _local_interlockedbittestandreset
#   define _interlockedbittestandset64 _local_interlockedbittestandset64
#   define _interlockedbittestandreset64 _local_interlockedbittestandreset64
#   include <intrin.h> // to force the header not to be included elsewhere
#   pragma pop_macro("_interlockedbittestandreset64")
#   pragma pop_macro("_interlockedbittestandset64")
#   pragma pop_macro("_interlockedbittestandreset")
#   pragma pop_macro("_interlockedbittestandset")
#endif

It should be okay to include this before or after WinNT.h.


        

        

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